Vacuum advance control mechanism



July 31, 1962 .1. c. NORRIS VACUUM ADVANCE CONTROL MECHANISM Filed May 9, 1960 INVENTOR. James C. Norris Fig.2

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Filed May 9, 1960, Ser. No. 27,802 1 Claim. (Cl. 123-117) This invention relates to apparatus for controlling the ignition timing of an internal combustion engine and particularly the vacuum advance control mechanism for controlling the movement of a breaker plate of a distributor.

The ignition timing of internal combustion engines in many instances is brought about by a distributor that includes mechanism for providing both a centrifugal spark advance and .a vacuum advance. The centrifugal spark advance is in proportion to the speed of the engine whereas the vacuum advance apparatus usually includes a vacuum motor which rotates a breaker plate of the distributor in accordance with vacuum conditions in the intake manifold of the engine.

In past vacuum spark advance arrangements, it has been common practice to connect the vacuum motor that operates the breaker plate of the distributor to a passage formed in a carburetor housing that is located on the intake or atmospheric side of a throttle valve when the throttle valve is set for engine idling. With this arrangement, the vacuum motor is connected essentially with atmospheric pressure when the throttle valve is set for engine idle and there therefore is no spark advance at engine idle.

In contrast to the above described arrangement, it is an object of this invention to provide a vacuum advance arrangement wherein a slight vacuum advance is achieved at engine idle, thus bringing about better idling of the engine.

A more specific object of this invention is to provide a vacuum advance arrangement wherein the vacuum motor that drives the distributor breaker plate is connected with two passages formed in a carburetor housing which have inlets positioned on opposite sides of a throttle valve when the throttle valve is in a position to provide engine idle. With this arrangement, the diaphragm of the vacuum motor is acted upon by suflicient vacuum at engine idle to provide some vacuum advance.

Another object of this invention is to provide a vacuum advance arrangement wherein a spark advance is achieved at engine idle and wherein the amount of this advance is adjustable. This object is carried forward by connecting the vacuum motor that provides the vacuum advance with two passages having theirinlet sides positioned on opposite sides of the throttle valve of a carburetor when the valve is set for engine idle and further providing means in one of the passages for adjusting its flow capacity.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 illustrates a vacuum advance arrangement for an internal combustion engine made in accordance with this invention.

FEGURE 2 is a sectional view taken along line 2-2 of FIGURE 1.

Referring now to the drawings, the reference numeral 19 generally designates a distributor for controlling the ignition timing of an internal combustion engine. The distributor includes the usual base 12 which carries a 13,94,962 Patented July 31, 1962 ice breaker plate 14. A shaft is provided which is driven by the internal combustion engine and which drives a cam 16 that cooperates with a breaker contact set 17 carried by the breaker plate 14. The set includes the conventional breaker arm 17a, rubbing block 17b, and breaker points and 17d. The breaker platej14, as in conventional practice, is rotatable with respect to the cam 16.

The breaker plate 14 is rotatably driven by a vacuum motor 18 which has the usual spring 1? and diaphragm 21, the diaphragm being connected with a rod 20 which in turn is connected with the breaker plate 14 to rot'atably drive the same. The spring 19 Within the vacuum motor 18 normally urges the rod 20 in a direction to shift the breaker plate 14 to its fully retarded position. When vacuum is applied to the vacuum motor 18, the rod 20 will be shifted to thereby shift the breaker plate 14 and advance the spark. The distributor 10 may be of any conventional type and may be of the type illustrated in the patent to Norris et al., 2,913,543.

The reference numeral.22 has been used to generally designate a carburetor having a housing 24 formed with an air intake passage 26 and an outlet passage 28 which communicates with the intake manifold 29 of an internal combustion engine. A throttle valve 30 is provided which is pivotally mounted and which is pivoted or rotated when the accelerator pedal of a motor vehicle is depressed.

The housing 24- of the carburetor 22 is formed with passages 32 and 34 which are both connected with the pipe 36 via a fitting 37. t can be seen that the pipe 36 connects both of these passages with the vacuum motor 18. The passages 32 and 34 are so positioned that with the throttle valve in its full line idling position illustrated in FIGURE 1, the passage 32 is on the air intake or atmospheric side of the throttle valve whereas the passage 34 is on the intake manifold side of the throttle valve. The throttle valve in the full line position will provide an idling condition for the internal combustion engine, as it will be well known to those skilled in the art, .and it is thus seen that at engine idle, the passage 32 is connected with atmosphere whereas the passage 34 is connected with the intake manifold. It can be seen that the passage 34 has a diameter larger than that of passage 32 and may have its flow capacity varied by means that includes an adjusting screw 38 that is threaded into the carburetor housing and which has a nose portion to vary the flow capacity of the passage 34.

In the operation of this device when the throttle valve 30 is in the full line position illustrated in the drawing, the passage 32 is connected with atmosphere whereas the passage 34 is connected with vacuum. The combined efiect of this is to communicate sufficient vacuum to the vacuum motor 13 to cause the diaphragm 21 of the vacuum motor to be moved slightly and thus cause the rod 20 and the breaker plate 14 to be shifted. Rotation of the breaker plate slightly will cause the spark to be advanced to some degree at engine idle and the amount of this advance may be adjusted by adjusting the screw 38. It should be pointed out that this vacuum advance arrangement will work equally well where the adjusting screw is positioned in the passage 32 and no adjusting screw is provided in the passage 34. In either case, the adjusting screw is adjusted until a desired vacuum advance is achieved at engine idle and this vacuum advance in either instance is due to the combined connection of the pipe 36 with both the atmospheric and vacuum sides of the throttle valve 30.

When the throttle valve 30 is opened to the dotted line position or further, both passages 32 and 34 are connected to essentially the same pressure, that is, both passa es 32 and 34 will be connected with vacuum so that the vacuum motor 18 will now be influenced by the combined efiect of these passages both being connected with vacuum. The net efiect of this is the same as if one single passage wereprovided having the flow capacity of the two passages since both passages are now connected to essentially the same pressure conditions. vacuum motor will operate to provide the required vacuum advance during changing vacuum conditions in the intake manifold of the engine at various operating conditions of the engine. It thus can be seen that the vacuum advance arrangement of this invention provides some vacuum advance at engine idle but does not adversely efiect the operation of the vacuum advance arrangement at other load conditions of the engine such as at full throttle or positions between engine idle and full throttle.

While the embodiments of the present invention as herein disclosed, constitute a preferred form it is to be understood that other forms might be adopted.

What is claimed is as follows:

In combination, an internal combustion engine having an intake manifold, a carburetor having a chamber, a

Because of this, the

manually adjustable means for increasing and decreasing the flow capacity of one of said passages, a distributor having a rotatable partfor controlling the ignition timing of said engine, a vacuum motor for shifting said rotatable part, and means connecting said passages with said vacuum motor, said passages being sized such that at least some spark advance can be obtained when said throttle valve is fully closed by adjustment of said adjustable means.

References Cited in the file of this patent UNITED STATES PATENTS 2,183,747 Jennings Dec. 19, 1939 20 2,336,424 Schachenman Dec. 7, 1943 2,376,973 Mallory May 29, 1945 

